A few months ago, a Trump GOP nomination seemed impossible. But now, it seems inevitable.

When Donald Trump announced his campaign, I thought there was no way anyone would support him after the comments he made about Mexican immigrants. When he offended women with his comments about debate moderator Megyn Kelly, I thought his campaign would be over. When he called for a ban of all Muslims, I thought that would be the last straw. But again and again, Trump has gained more support.

"There is really only one reason Trump supporters should not support Trump: He is not qualified."

We've been telling Trump supporters that he is a racist, a sexist, and a bigot, as reasons for why Trump should not and cannot be the next president of the United States. However, we've failed to realize that supporters of Trump support him because he is the embodiment of their own ideology. Trump's unexpected rise as the GOP front-runner is because there is a large population of Americans who feel displaced, who feel like their country and their way of life is being taken away from them. Trump has offered this population an unashamed and unfiltered rallying cry.

We have been going about this all wrong. There is really only one reason Trump supporters should not support Trump: He is not qualified.

And by that, I mean that he is not qualified to deliver on any of his promises.

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Republican presidential candidate Donald Trump waves to the crowd after a rally March 1, 2016 in Louisville, Kentucky.

One of the major pillars of his campaign is his building of the now infamous "big, beautiful wall" along the Mexican border. The wall got 10 feet taller after ex-Mexican President Vicente Fox said he was "not going to pay for that f--ing wall."

I understand some people are excited about the wall. In their mind, the wall would keep all those "illegals" away from American jobs. While Trump has said repeatedly that Mexico will pay for the wall, how does an American president make another sovereign nation pay for anything? Trump has yet to outline a concrete plan.

The only vague answer we've been able to get from Trump is that he plans to use the trade deficit with Mexico as a way to pressure Mexico to pay for the wall. The U.S. does have a trade deficit with Mexico, but it is also true that Mexico was our third largest trade partner in 2015. In 2015 alone, our total trade of goods with the rest of the globe was $3.7 trillion, of which more than 14 percent ($ 531.1 billion) was with Mexico. He puts that at risk.

Let's assume that Trump can stop all Mexican products from coming into the U.S. ($294.7 billion in 2015) to pressure Mexico to pay for the wall. (Even this is a stretch, as there are trade agreements in place that would have to be suspended with the approval of Congress. But let's assume that for now.)

Let's not forget that Mexico can also refuse to import American products in retaliation for their own products not being allowed into the United States. Products that are made in American factories that employ U.S. citizens. In 2015, we exported $236.4 billion to our neighbors to the south.

A 2011 report by the Wilson Center found that there are 6 million U.S. jobs that depend on trade with Mexico. More than 1 million of those jobs are in two states — California and Texas.

And it's not just border states that depend on trade with Mexico. South Dakota, New Hampshire, and Nebraska also send more than 20 percent of their exports to our southern neighbor, according to the Wilson Center.

Mexico is the largest supplier of car parts that are then used to build cars in plants in the U.S. where American citizens are employed. The Wilson Center found that Detroit alone exports $10.9 billion in cars and car parts to Mexico.

How would Trump deal with a potential loss of 6 million jobs or more? Is it worth destroying the economies of Michigan, California, and Texas?

All this … over a wall.

Yes, Mexico's economy is certainly going to suffer if Mexican products cannot be imported into the U.S. At this point, net migration from Mexico is near zero, as there are as many Mexicans leaving the U.S. as there are coming in. But what has driven millions of immigrants over the border in previous years? A search for economic opportunity, a better life. If Mexico's economy worsens, we will see a reversal of recent migration patterns. Because, while Trump pressures Mexico by cutting off trade, Mexicans won't be able to find jobs in Mexico, which will send them here.

So while all of us anti-Trump think he should not be president because of his hateful speech and rhetoric, Trump supporters should just ask themselves one simple question: Is he qualified to deliver on his vague promises to you? On any?

Commentary by Julissa Arce, the author of the forthcoming book, "My (Underground) American Dream" (Sept. 13, 2016). Arce made national and international headlines when she revealed that she had achieved the American Dream of wealth and status working her way up to vice president at Goldman Sachs by age 27 while being an undocumented immigrant from Mexico. Follow her on Twitter @julissaarce.

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